Electrode Functionalization and Membrane Engineering for a Tunable Interfacial Nanopore Device

This thesis addresses the development and optimization of a tunable interface nanopore (iNP) device for single-molecule protein sensing. In contrast to conventional solid- state and biological nanopores, the pore is defined by the geometric interaction between a soft polymeric membrane and a nanostructured glass blade, enabling real-time size modulation without nanolithography. This approach reduces fabrication complexity, enhances adaptability to different analytes, and improves compatibility with microelectronic platforms. The work focused on two main aspects: (i) polymer membrane engineering, aimed at reducing thickness and improving actuation efficiency, and (ii) electrode functionalization, to reduce impedance and increase charge storage capacity (CSC) for improved signal-to-noise ratio (SNR). Membranes fabricated in polydimethylsiloxane PDMS and thermoplastic polyurethane (TPU) with thicknesses down to ∼30 μm were compared to standard ∼100 μm PDMS. Atomic force mi- croscopy indentation tests showed that TPU exhibited the highest stiffness (Young’s modulus ∼1.1 MPa), followed by thin PDMS (∼0.83 MPa), while thick PDMS was the softest (∼0.52 MPa). Thinner membranes transmitted actuation forces more effec- tively to the microfluidic channel region, supporting finer nanopore diameter control. Electrochemical coatings were systematically evaluated. Pt nanograss (potentiostatic deposition at -0.2/-0.4 V for ∼300 s) reduced impedance at 1 kHz by ∼60 % and in- creased CSC up to +267 %. Prolonged deposition enhanced CSC further (up to +650 % at 900 s) while impedance benefits saturated. Pt black (galvanostatic deposition) provided the strongest enhancement, with impedance reduced by ∼70 % across all currents and CSC increases exceeding +2000 % at -50 mA, despite exhibiting a some- what uneven morphology. Moderate plating currents (-0.5 to -5 mA) yielded more homogeneous coatings with robust performance. In contrast, PEDOT:PSS layers detached rapidly under the tested chip design, showing no measurable improvement; preliminary tests on modified electrodes suggested that improved adhesion could unlock its potential. Overall, the results demonstrate that thin TPU membranes and Pt black or Pt nanograss coatings offer the most promising combination for enhancing interface nanopore performance. These advances pave the way toward scalable, reproducible, and high-sensitivity devices for single-protein detection and sequencing.